It's funny - the cards that tend to elicit the strongest emotional responses or have the worst reputations actually possess some of the most down-to-earth, productive advice.
There's always that moment of palpable trepidation when an inexperienced querent receives The Devil in a reading. There are different ways for readers to deal with any (understandable) concern and my go-to method is to actually focus on The Devil first, regardless of where it's come up in the spread. There are two main reasons for this. The first is to immediately 'break the ice' of the card and dispell any bad juju the querent might have about it. The second is because I usually feel it's one of the strongest cards in any spread (and I'm not into convention - I read the strongest cards and give the most clear messages first rather than reading in position order). Of course all cards are defined by the cards around them and The Devil seems to always be in an intriguing place in the spread. (I also love it when The Devil turns up in a one card reading. There's so much meat to the bone with this card, it makes it really easy to get a lot of guidance out of it.)
Years ago when I was reading with The Mythic Tarot deck, The Devil was represented by Pan. The card's message was all about giving in to natural instincts and focused on how Pan has been misunderstood in modern times and associated with the Christian idea of evil. My mum (whose cards I've read for over a decade now) never liked this interpretation. She felt that it only dealt with the surface of the true card meaning and 'glossed over' the darker elements of the message. The Devil in The Rider Waite deck does seem to offer a more practical focus, centering on emotional blockages, denial of feelings and breakdowns in communication. I think, for me, the card has also come to represent the Freudian issues of imprints from childhood having a negative effect on the present situation.
The Devil is a useful draw when there is a challenger in the querent's life. It speaks of the importance of standing by your principles or outlook when there are those who oppose it. This links nicely in with another strong message: what is it that you hold on to despite the fact that it's making you unhappy? Which parts of your personality or material possessions are you better off saying goodbye to and what's stopping you from letting go of them? This card can also address a rather ugly truth about the querent, since it does have its links with victimhood and self-pity. Blaming others or outside circumstances for your own personal failures could be an issue if this card is drawn. Seeing our challengers as devils who taunt us needlessly can allow us to fall into a cycle of blame and lead us to justify our inability to solve matters instead of being proactive. This is the perfect card to remind us that it's better to see our challengers and adversaries as figures who eventually lead us into self-discovery and strength rather than to demonise them and, in the process, make ourselves stubborn or bitter.
The card is a blessing in disguise for both the reader and the querent but it does touch on some uncomfortable truths about the importance of making changes from within rather than always focusing on outer circumstances and the failures of others. It almost encourages us to hold a mirror up to ourselves before we assume that all of our issues are caused by elements beyond our control.